Vulnerability Monitor

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CVE-2019-18425

An issue was discovered in Xen through 4.12.x allowing 32-bit PV guest OS users to gain guest OS privileges by installing and using descriptors. There is missing descriptor table limit checking in x86 PV emulation. When emulating certain PV guest operations, descriptor table accesses are performed by the emulating code. Such accesses should respect the guest specified limits, unless otherwise guaranteed to fail in such a case. Without this, emulation of 32-bit guest user mode calls through call gates would allow guest user mode to install and then use descriptors of their choice, as long as the guest kernel did not itself install an LDT. (Most OSes don't install any LDT by default). 32-bit PV guest user mode can elevate its privileges to that of the guest kernel. Xen versions from at least 3.2 onwards are affected. Only 32-bit PV guest user mode can leverage this vulnerability. HVM, PVH, as well as 64-bit PV guests cannot leverage this vulnerability. Arm systems are unaffected.

Published

2019-10-31T14:15:12.150

Last Modified

2024-11-21T04:33:14.447

Status

Modified

Source

[email protected]

Severity

CVSSv3.1: 9.8 (CRITICAL)

CVSSv2 Vector

AV:N/AC:M/Au:N/C:C/I:C/A:C

  • Access Vector: NETWORK
  • Access Complexity: MEDIUM
  • Authentication: NONE
  • Confidentiality Impact: COMPLETE
  • Integrity Impact: COMPLETE
  • Availability Impact: COMPLETE
Exploitability Score

8.6

Impact Score

10.0

Weaknesses
  • Type: Primary
    CWE-269
Affected Vendors & Products
Type Vendor Product Version/Range Vulnerable?
Operating System xen xen ≤ 4.12.1 Yes
Operating System debian debian_linux 9.0 Yes
Operating System debian debian_linux 10.0 Yes
Operating System fedoraproject fedora 29 Yes
Operating System fedoraproject fedora 30 Yes
Operating System fedoraproject fedora 31 Yes
Operating System opensuse leap 15.0 Yes
References